A music track (called "ParallaX") was created with only one synth sounds (SYNTH1). SYNTH1 is a free VST. 
Can be found here : https://daichilab.sakura.ne.jp/softsynth/index.html.

ParallaX

Pushing music that we love <3
https://supreme-boutique.com

I barely make music anymore so this is mostly used to host my old tracks and One Synth Challenge submissions. And random bits/bobs for demonstration.

Hello, SoundCloud crew. I create all my music from the ground up. ZERO A.I. (Except for the tracks Jamaica and Castlevania versions, which, I altered the original notes from pre made template.)  I am an experimentalist with tones of synthwave and ambient thrown in to the mix. I hope you can enjoy some of my tracks.  

I use FL Studio most of the time.
GEAR BEHIND THE SOUNDS.
FL STUDIOS
FLKEY49
NOVATION LAUNCHPAD PRO
ROLAND RD-88
ALESIS V49
SCARLETT SOLO
GRETSCH ELECTROMATIC GIT.
FENDER MUSTANG III

ParallaX

Patrick de ZUND